This invention relates to a programmable timing controller for synchronizing the operation of one or more sections of a glassware forming machine or other plural-sectioned machine with one another and with machine components common to all individual sections.
The individual section glassware forming machine ("IS machine"), which is well known in the art, comprises a plurality of individual sections. The individual sections perform sequentially timed functions in synchronism with one another in a phased relationship. Gobs of molten glass are acquired in sequence from a shear and feeder mechanism and as one of the individual sections is receiving a gob, another individual section is delivering a finished glass container to a conveyor system. At the same time, other individual sections are engaged in various functions that are intermediate between the receiving of a gob and the delivering of finished glass container to the conveyor. Such a glassware forming machine is disclosed in Ingle U.S. Pat. No. 1,911,119.
It is necessary to accurately control the timing of various IS machine operations. It is well known to time the mechanism operations common to all of the individual sections of an IS machine by a drum having cam members, called buttons, movably attached about its surface. The drum is rotated by a motor which may, also, drive the gob feeder mechanism. The cam members selectively activate valves in a valve block to control fluid pressure to cylinders which operate the various operating components of each of the individual sections of the IS machine. This arrangement is, also, disclosed in Ingle U.S. Pat. No. 1,911,119.
However, the process of positioning the cams on the timing drum to implement or modify function timing sequences is inexact, cumbersome if not dangerous and time consuming. Such a timing apparatus further to prone to mechanical wear leading to irregularities in the forming operation, resulting in unacceptable glass containers. Consequently, substantial efforts have been made to develop an electronic timing and synchronizing control system to help overcome such drawbacks. Such an automatic control system is disclosed in Quinn et al U.S. Pat. No. 3,762,907 and Kwiatkowski et al U.S. Pat. No. Re. 29,642. The control system disclosed in these patents include a machine cycle position indicating means which in the embodiments disclosed was the shaft for driving the gob shears. In addition a timing means was responsive to the cycle position indicator for generating a digital signal indicative of the machine cycle position. In the embodiments disclosed, this was a shaft encoder. Thus in the embodiments disclosed, an electro-mechanical drive system was provided. The appreciable amount of jitter experienced with the electro-mechanical shaft encoder, sometimes as high as five or ten percent, adversely effects the accuracy of the timing controller and limits the operating speed. In a recently issued U.S. Pat. No. 4,145,204 to Farkas a control system is disclosed which also includes a cycle position indicating means and a timing means responsive thereto for generating a signal indicative of the machine cycle position. In Farkas the cycle position indicating means is the inverter which drives the motors and the timing means is a signal generator which is responsive to the output of the inverter. More specifically, in Farkas, a gob feeder and distributor supplies gobs to the individual sections at a predetermined rate proportional to the frequency of the power supplied by an inverter drive. A timing circuit is responsive to the frequency of the inverter output to generate clock signals which are applied to a machine control circuit for controllably actuating the functions of an associated individual section. The timing circuit also provides a timing reset signal to initiate the machine cycle. Accordingly, the machine speed, function timing, and cycle initiation are synchornized with one another, and the gob feeder and the gob distributor are phased (with reference to the reset signal) such that a gob is distributed to the individual sections at the required times in the machine cycle. More accurate control of the machine cycle is facilitated by providing a gob detector circuit and sensor, which detect the presence of a gob at the mold. Responding to the output of the gob detector circuit, the control circuit supplies a minor correction to the section timing, if needed. The Farkas apparatus includes a plurality of drive motors which must be phased with one another.
Reference also is made to commonly assigned copending U.S. application Ser. No. 281,466, of Haynes et al, filed July 8, 1981 which relates to a method and apparatus for glass factory control. The present invention can be conveniently utilized with the Haynes et al apparatus which includes a programmable apparatus responsive to the frequency of an oscillator for generating a synchronous timing signal at a frequency which provides 360 pulses per machine cycle. A timing reset signal for initiating the machine cycle is derived from the timing signal. The apparatus also generates a synchronous drive signal which is applied to an inverter system for controlling the speed of respective motors (gob distributor, shear, and conveyor motors in the Haynes et al apparatus). A feedback loop from the gob distributor motor to the inverter system enables proper control and stability.
There is thus still a need for an improved timing controller adapted for use in an IS machine (or in other types of machines having sequentially timed steps) which avoids jitter contaminated timing pulses and eliminates the need for plural mechanical drive motors and sensors and sensor detection circuitry. Further, there is need for such an improved timing controller to be programmable to automatically provide a machine speed setting and to dynamically vary that setting during operation.